The subject of Janine Hosking's documentary Mademoiselle and the Doctor is intelligent, charming and, at 79, as fit as a fiddle.

She is also in the process of planning her own death.

Hosking's film, screening as part of the 51st Sydney Film Festival, follows the final weeks of Lisette Nigot, a healthy Frenchwoman living in Perth who wants to die before turning 80. The film documents her decision and the involvement of euthanasia activist Philip Nitschke.

Hosking admits the topic of her film is controversial, but says she was drawn by Nigot's character. "She just captured me absolutely. Why is she thinking like this? I really, really liked her and I found it extraordinarily sad that she carried it through," Hosking said. "But that doesn't lessen her right to do it, in my eyes."

Dr Nitschke said Nigot's case had had a profound impact on him. "She challenged my concept that this [euthanasia] was reserved for someone that was seriously ill," he said.

"My philosophical position is, yes, mature, rational people over a certain age - which remains undefined - should have access to the ways and means of a peaceful death. And that's all people, not just sick people."

At the debut screening of the documentary yesterday, Hosking and Dr Nitschke fielded questions about the "peaceful pill" that can be manufactured at home and bring about painless death. In the audience was NSW Greens upper house MP Ian Cohen, whose bill advocating voluntary euthanasia for the terminally ill was defeated last year.

Anyone found guilty of assisting a person's suicide can face a long jail term, and Dr Nitschke admitted he was concerned the film could lead to his arrest.

"Yes, it worries me," he said. "The safe thing is to do nothing - but if you want to see change in society, there's obviously a need at times to move closer to the cliff and take some risks."

The Queensland Police Service is still considering whether to lay charges against the 21 people who witnessed the 2002 suicide of Gold Coast woman Nancy Crick.

Mademoiselle and the Doctor is screened again at 4.35pm today at the State Theatre as part of the Sydney Film Festival.